Atomic and Ionic Radii, Bond length and Measurement of Radius.ppt

Crystallography is the branch of science which deals with all the aspects of crystals, that is, their formation from the melts, internal structure and external shape or morphology. An elementary knowledge of crystallography is essential for all those who have to deal with minerals in one way or another such as mining engineers, civil engineers and engineering geologist Atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons . The electrons of an atom are bound to the nucleus by the electromagnetic force. An atom containing an equal number of protons and electrons is electrically neutral, otherwise it has a positive charge if there are fewer electrons or negative charge if there are more electrons All matter is composed of extremely small particles called atoms. All atoms of a given element are identical in size, mass, and other properties. Atoms of different elements differ in size, mass, and other properties. Atoms cannot be subdivided, created, or destroyed. Atoms of different elements can combine in simple, whole-number ratios to form compounds. In chemical reactions, atoms are combined, separated, or rearranged. The atomic radius of an element is basically the size of the atom. We can determine the atomic radius by finding half the length between the nucleus’ of two atoms of the same elements. The size of atoms (and therefore the atomic radii) increase as we go down groups on the periodic table (since more energy levels are added), but as we go to the right, the size decreases because… Electrons are being added to the same shell, which does not change the size of the atom, but protons are also being added to the nucleus, which pulls the electrons inwards towards the center, decreasing the radius.